Engine overheating audi 4.2 a8 1999

Hi

Car running well but engine over heating after 10 miles
When heater is on full engine returns to normal temp
no obvious oil leak
fan does not seem to come on
cooling fluid ok
Engine check system reads ok

1 Suggested Answer

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Mar 28, 2010 - Temp gauge runs hot but car makes no heat. ... Honda-Tech Member ... I figured my theromstat was going bad so I replaced that and it did nothing. ... Any help would be awesome, im losing my patience fast and I have a real big hammer ... This is between the engine and the heater core (under the hood).

Has coolant level been going down in return reservoir at all, as in have you had to add coolant recently to bring it up to top level? Have you tried running engine from cold, with heater on and let it run up to normal temperature with cap off return reservoir? If not do so, and watch level in reservoir and if it goes down, add as needed until engine running at normal, and not overheating. Allow rad fan to kick on & off a few times before re-installing cap on reservoir. Pay close attention to engine temp while doing this. If it goes high, shut it off and let cool. Be careful, my son's Passat just had overheat problem and turned out to be impeller on water pump ( internally) was spinning on shaft of pump. Thermostat is certainly a consideration if coolant is full, and all air bled out. Keep me posted on what happens when you run with cap off and keep reservoir full. Don't forget, heater on while doing this.

Overheating Due to corrosion block in Water Pump on Erratic engine coolant temperature or intermittent overheating can be caused by corrosion inside the water pump. ...Either condition reduces coolant circulation resulting in engine overheating.

Sounds like you have coolant leak if you are loosing coolant or a bad thermostat. I would replace the thermostat, they run about $10. The other fan is an aux fan and will only run when the a/c unit is on.

run it and let it get hot (not to the point of overheating just let it warm up to normal or slightly above normal). put your hand near the upper radiator hose, if you feel not heat, touch it, be careful as it may be hot. if it is not hot at all but the engine is warmed up it is the thermostat, the thermostat is located where the upper radiator hose connects to the motor, usually a 2bolt metal fitting, if this is the case just replace the thermostat.

When an engine is overheating and then the temp drops on the guage, it's usually a sign that the coolant is not touching the temp sensor. There's no coolant in the engine. Putting water in the overflow tank won't solve this. Take the radiator cap off after the engine cools and put coolant in the radiator. you might have to crank the engine and do this several times, as the engine can develop air pockets that won't allow the coolant to travel inside the engine. If you don't see any leaks, and it still uses coolant, you've probably got a blown head gasket. Check for water on the plugs, check cylinder compression. If it slowly uses coolant, try putting a large box of pepper in the radiator or some of that radiator seal copper flakes.